Intra-aortic counterpulsation employing an inflatable balloon within the aorta has become a recognized method for assisting a failing heart and augmenting the flow of blood to the body's various circulatory beds. It has also been shown that uni-directional movement of blood, preferentially to the coronary arteries which nourish the heart muscle itself, is of particular value in aiding the recovery of a failing heart to an adequate and self-sustaining state.
An ordinary, simple, single-chambered balloon was the first type of balloon employed for intra-aortic counterpulsation. However, this simple type of balloon does not insure any degree of preferential flow toward the mouths of the coronary arteries. Rather, it provides omnidirectional flow, i.e., the blood displaced as the balloon inflates will flow toward those vascular beds of lowest resistance. Thus, some blood may flow back within the aorta toward the heart and coronary arteries and some is propelled forward toward the abdomen and lower extremities.
One method of providing uni-directional flow or preferential flow back toward the heart and coronary arteries is disclosed in U.S. Pat. No. 3,692,018. That patent discloses two balloons of different size separated from each other and mounted on a single tubular conduit through which gas is pumped. The tubular conduit passes within both balloons and has holes opening into both balloons so that they may be inflated by the gas pumped through the tube. They are inflated so that the smaller balloon inflates first to occlude the aorta, and the larger balloon second to pump blood away from the occluding balloon. To insure inflation of the occlusive balloon prior to the larger pumping balloon, an obstructing member is placed within the tubular conduit at a point inside the occlusive balloon so that gas first enters the occlusive balloon to inflate it, then flows back into the tubular conduit through holes on the other side of the obstructing member, and continues within the tubular conduit until it reaches holes communicating with the larger pumping balloon, which is then inflated.
There are several disadvantages of this device. First, the pattern of gas flow in and out of the tubular conduit through small holes tends to be turbulent flow, thereby requiring more pumping pressure or time to inflate the balloons. Second, the full diameter of the tubular shaft must be maintained along the axis of both balloons in order to convey the gas. This results in a bulky device to insert into the patient's artery since the ballons must be wrapped around a tubular conduit of full diameter. Third, because of the obstructing member, the occlusive balloon must always be placed on the tubular conduit closer to the pump than the pumping balloon since gas must exit from the occlusive balloon back into the tubular shaft beyond the internal obstructing member, in order to reach the pumping balloon. Because of this order of the two balloons along the tubular shaft, the device can only be used when it is to be inserted into the aorta from the lower portion of the human body, e.g., via the femoral artery in the thigh, so that the pumping balloon lies closer to the heart and the occlusive balloon more distal. This same device cannot be employed for preferential pumping toward the heart and coronary arteries when the operator desires to insert a device from above, as via the brachial or axillary artery, since the device would come to reside in the aorta with the two balloons in the opposite direction or sequence from that required for preferential coronary blood flow, i.e., toward the heart.